Impossible Is Suddenly Harder to Define
by TwueWuvIsMyDivision
Summary: "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." However after the appearance of a certain Captain Jack Harkness, "impossible" is suddenly much harder to define.


**This takes place after Torchwood's Children of Earth and a few months after BBC Sherlock's pool scene in the beginning of series 2. The Doctor will be appearing in the future and not much of Torchwood is really going to be talked about, so I'm making this a Doctor Who/BBC Sherlock crossover instead of a Torchwood/BBC Sherlock one. **

**I will probably get timeline/random details wrong on occasion. I apologize in advance. **

**For Emma because she won't let me not write this. You can blame/thank her. **

-x-

**Chapter One: Captain Jack Harkness**

Sherlock was starting to get bored. John may not be as skilled as the consulting detective at reading people, but over the time he had lived and worked with the other man, he had gotten good at reading his flatmate. Currently, the boredom was making itself known in the way that Sherlock had refused to move from the couch and was becoming unnaturally still, his hands folded in his thinking pose, his eyes slightly unfocused. John rolled his eyes in amused exasperation at the fact that the man wasn't dressed for the day despite it being past three in the afternoon. It didn't look likely that a case was going to arrive at their doorstep anytime soon, and so Sherlock had deemed clothes that normal people wear during the day unnecessary.

John needed to think of something quickly, before the "calm before the storm," as he mentally labeled Sherlock's current mood, broke and all hell let loose. Probably with many loud explosions and general destruction of their flat. His thoughts briefly flirted with the remembrance of the Cluedo game that lay among the piles of random objects that were strewn around the flat. Playing Cluedo with Sherlock would probably be an entertaining way to keep the man's mind occupied.

It was certainly entertaining when John had first found the game lying forgotten under a mound of books that lay under a table. He hadn't said anything, only held it up for Sherlock to see and raised a questioning eyebrow. Privately, John had felt that the look on Sherlock's face at that moment was worth a month of experiments crowding their kitchen. A slight pink hue had appeared on the cheeks of the normally completely composed consulting detective, and he had muttered something about "Christmas present" and "Mummy" and "gag gift," before retreating quickly back into the kitchen.

Amused, John had decided not to press the issue, but filed the reaction in his almost empty mental folder labeled "Blackmail on Sherlock."

Before he could get up to dig out the board game however, the doorbell rang in two short bursts, the second longer than the first. He took the time to ponder about the fact that he might be spending too much time with Sherlock if he was making note of specifics such as how the doorbell was rung. Somehow, he very much doubted that it could actually led to any meaningful conclusions.

He looked over at Sherlock. Sherlock continued to not move. John opened his mouth to inform human shaped inanimate object that he probably had a client and should probably get the door because it was his client, and that he, John, was quite comfortable where he was and not his housekeeper either.

"It's not a client," John's mouth closed. "If it was a client they would have rung once with a short, less than half a second probably, and hard press to the doorbell."

Okay, so maybe one could deduce something about a person from how they rang the doorbell. Admittedly, John was impressed, but seeing as it also meant that Sherlock would not be answering the door, he was also quite annoyed. Sherlock wasn't finished.

"Two rings suggests that the visitor is slightly impatient, maybe slightly stressed or eager, but also comfortable enough with the person he or she is visiting to outwardly show the impatience. Obviously if it is a personal visit, it is much more likely that they are visiting you and not me. Therefore you should get the door," Sherlock paused, "And I would hurry up. They're probably getting tired of waiting."

"Fine, you git. You probably made that up so you wouldn't have to get up," He pushed himself up from his chair and made his way to see who was visiting.

The doorbell gave another impatient ring before John opened the door. Contrary to Sherlock's predictions, the man standing in front of him was not familiar in the least, and John was reasonably sure that he would have remembered this man. He was definitely memorable with bright blue eyes and an attractive smile that showed more teeth than John would have thought possible. A long heavy coat gave the man a sense of importance, which reminded John reluctantly of Sherlock.

"Can I help you?" He hoped that the man was a client and this was not a personal visit so Sherlock could be wrong for once. It would do him good.

The man's grin grew wider, and his whole demeanor gave off a friendly vibe.

"Hello, I'm Captain Jack Harkness," The voice was smooth and American, and John felt the sudden urge to inform the man that he was not gay. "I'm guessing from your blog that you're Doctor John Watson? I'm here to see Sherlock Holmes. Unless I've got the wrong address of course," He paused. "Of course if I haven't got the right address, it might not be a total loss."

That was definitely a wink. To John's horror, he felt his face heat up slightly in embarrassment.

"Er, yes. I am John Watson. This is the residence of Sherlock Holmes. Are you a client?" Captain Harkness shrugged.

"Not exactly. It's mostly a personal visit with a little business added in."

Damn. Sherlock had been right that it was personal. John moved to the side to let in their guest.

"I apologize in advance for his state of dress and anything he may say or do," He said dryly as the captain moved past him. He was rewarded with a laugh and a knowing roll of blue eyes. Apparently, he was well aware of Sherlock's habits.

Sherlock hadn't moved from his place on the couch when they entered the flat. His eyes were closed now though. John gave the bare feet that were crossed and resting on the arm rest of the couch a nudge as he passed to take his regular seat in his chair.

"Sherlock, there's a Captain Harkness here to see you. Which means you're getting the bloody door next time regardless if it's for me or not."

"Jack, please," the captain corrected him, giving him another slightly overly friendly smile.

John was about to respond when Sherlock came alive rather violently. He sat up in an abrupt, almost panicked, manner, his eyes wide and his mouth opening and closing as if he were attempting to find the right words but couldn't. For once in his life, Sherlock seemed speechless. This was better than finding the Cluedo game. Finally after a moment of Jack grinning at him in open amusement, he seemed to decide on a warning look.

"No," He said simply, narrowing his eyes at the other man.

"I have no idea what you are talking about," Jack was the picture of innocence.

"No. Leave John alone."

Jack let out a laugh.

"Good to see you too, Sherlock."

"Good to see me? It's not my fault you haven't visited in four years," He slumped back against the couch cushions, giving Jack a look that John would almost classify as a pout.

John was officially lost at this point. He had been in the middle of too many of the Holmes brothers spats to recognize the same signs showing up here, so he did the intelligent thing and got comfortable in his chair to watch it play out. By now, his curiosity was burning. Only Mycroft and John himself treated Sherlock with this level of familiarity.

"_My_ fault?" repeated Jack, raising an eyebrow. He settled himself on armrest of Sherlock's chair, facing the couch. "Where were _you_ at Christmas two years ago?"

"Busy," a dismissive hand waved away the question.

"And your schedule is quite a bit more flexible than mine has been. You could have easily come to visit me in Cardiff anytime."

"Cardiff is dull." John stifled a grin at the look of pure exasperation that Jack gave the consulting detective.

"Sherlock, we both know that is completely untrue."

"Yes, well, I don't see how you are suddenly able to safely take time from your job now. You were never able to before."

A sudden tension seemed to spread across the room. Jack's grin faltered for a moment, and Sherlock was sitting up again, examining the other man closely.

"The rift closed. There's not much for me there anymore," His grin was back at full power, but even to John it looked forced. To John's growing alarm, Sherlock actually looked distressed. No one said anything for a moment. Then Jack broke his eye contact with Sherlock and cleared his throat.

"What happened?" Sherlock's voice was uncharacteristically soft. John shifted in his seat. He wanted nothing more than to get up and leave the room and the sudden tension that had reached the point of being stifling. He was invading on something that was not his business. Something that was nowhere near his business. Still, he stayed in his seat, guilt staining his curiosity about Sherlock's past.

There was a pause. Jack said nothing. His eyes were fixed almost unblinkingly at the bright yellow smile that defaced the wall.

"I know the rift wasn't the only thing tying you to Cardiff, and it's rather obvious that you are not just taking a vacation from it."

The tension lifted briefly as Jack let out a snort and met Sherlock's gaze again. "I'm not going to ask how it is 'obvious' that I'm not taking a vacation."

Silence again. Jack's eyes moved again to the wall, and his smile disappeared completely.

Finally, Jack sighed and ran a hand through his hair. When he finally spoke, it came out almost as a whisper. "Everything happened."

Sherlock hesitated. "Is Alice... okay?"

John stared at him in surprise. Sherlock's uncharacteristically imprecise wording seemed to be an effort to soften his words, which was something Sherlock hardly, if ever, did. Who was this American? And who was Alice?

Jack's sudden smile was bitter and held no sense of happiness in the slightest. "I'm honestly a little surprised you remember her at all, let alone her name."

Sherlock gave a flinch so small that most would miss it. Neither John nor Jack did. John was pleased to see that Jack immediately looked guilty.

"I'm sorry. That was completely uncalled for," Jack ran his hand through his hair again, "Alice is alive and healthy. She also hates me with all her heart and will never forgive me for the rest of my life, nor do I blame her in the slightest. She was my last strong tie to Cardiff."

"What about your team? I remember you talking about them on occasion," Sherlock was obviously not letting the matter lie. Usually this was the time that John would step in and stop Sherlock from going too far in his questioning. This time, however, John had no idea what to do. It was obvious that this Jack Harkness had no desire to talk about why he was no longer in Cardiff. He could see it in the tense and rigid lines in his shoulders in back, in the tightness in his lips, and by the way that he was still not quite meeting Sherlock's eyes.

John wasn't anywhere near as good at Sherlock at reading people's pasts, but he was a hell of a good reader of current emotions. Learning to read Sherlock had made everyone else seem like an open book. And right now, Jack Harkness was in distress.

However, this time he couldn't just jump in and pull Sherlock back. This was a personal matter, and, John reasoned, this Captain Harkness could probably take care of himself.

It appeared he could. Jack took a short deep breath, shoulders relaxing. A well-practiced smile slid back into its regular place. "I'd rather not discuss them at the moment. Come on, Sherlock, this is the first time we've seen each other in four years! Stop bringing up depressing things. Happy occasion, Locks, _happy_," He gave Sherlock a mock disapproving look and shook his finger at him.

John let out a rather loud snort at that. "_Locks_?" He said, eyebrows raised, looking first at Jack then at Sherlock who was supporting an impressive scowl. Sherlock decided not to acknowledge the nickname or resulting question.

"What are you doing here? You hate being in London. If you wanted a visit, you would have arranged something at Mummy's manor and forced Mycroft to bring me along," Sherlock had obviously decided to switch to his suspicious defense tactic, John noticed in amusement. He only tended to do that when John was in an unexplained good mood. Something about how "no one was in that good of a mood for no reason, so obviously you are planning revenge for the experiment in the sink," which was ridiculous in John's opinion and completely untrue.

Mostly.

Jack rolled his eyes. "Fine. Yes, I'm here for a reason, but I wanted to ask you both a few questions before I kidnapped you, in case my suspicions are unfounded and therefore do not need to be pursued." John suspected that Jack was slightly mocking Sherlock's formal and calculating way of speaking. He was beginning to like this captain.

Suddenly, Jack's manner turned completely serious. He met both Sherlock's and John's eyes with a grim expression.

"I need to talk to you about Moriarty."


End file.
